We have recently demonstrated that aldose reductase (AR), an enzyme that catalyzes the reduction of reactive oxygen species-induced lipid peroxidation-derived lipid aldehydes and their glutathione (GSH)- conjugates (GS-LDAs), is an essential mediator of oxidative stress-induced carcinogenic signals. Our results from the previous project period have shown that inhibition of AR prevents the growth of human colon cancer cells by inhibiting the expression of NF-?B-dependent inflammatory markers. We have also shown that inhibition of AR prevents growth of human colon cancer cells in nude mouse xenografts, as well as azoxymethane-induced aberrant crypt foci formation in a mouse model. Further, we have also shown that inhibition of AR prevents colon cancer metastasis by preventing cancer cell invasion, migration and adhesion, as well as angiogenesis. Although we have shown that AR-catalyzed reduced products of GS-LDAs, such as GS-DHN, transduce carcinogenic signals downstream to protein kinase C (PKC), the molecular mechanisms that regulate cellular redox homeostasis leading to carcinogenesis are not clearly understood. We hypothesize that lipid aldehydes and GS-conjugates mediate anti-carcinogenic and pro-carcinogenic signaling cascades that lead to colon cancer growth and metastasis. Our goal in this project is to determine the mechanisms by which AR-catalytic activity plays a critical role in the regulation of colon carcinogenesis using human colon cancer cells, isolated human colon cancer stem cells in vitro, as well as in vivo orthotopic mouse models. Our long-term goal is to develop inhibitors of AR as safe and effective preventive measures for colorectal cancer growth and metastasis. Our specific aims are to: 1) determine how glutathione-lipid aldehydes (GS-LDAs) regulate NF-kB and Nrf-2 pathways that mediate CRC cell growth/death; 2) elucidate how AR inhibition prevents growth and metastasis of human CRC biopsy samples and colon cancer stem cells implanted in athymic nude mice; and 3) determine how AR inhibition prevents the survival of colon cancer stem cells. Completion of this project will elucidate the molecular mechanisms by which AR regulates cellular redox homeostasis, carcinogenesis and tumor growth and metastasis, and lay the foundation for the use of AR inhibitors as novel chemopreventive drugs for colorectal cancer.